Transaction with others by sending and receiving an e-mail is generally performed. For example, according to an e-commerce (electronic commerce) system, transaction between a product seller or a service provider and a user is performed using an e-mail.
There maybe a case in which an e-mail is failed to be delivered to the addressee for a variety of reasons. For example, in cases where a user has set mail rejection, where a user has changed his/her mail address, and so forth, an e-mail from a product seller or a service provider may not be delivered to the user. In this regard, Patent Literature 1 discloses a technique for delivering a message to an addressee by means of a pre-registered alternative means (for example, a facsimile device, a beeper, and so forth) in a case where an e-mail cannot be delivered to the addressee.